Invasive Alien Plants in South Africa

Lesley Henderson
T; Pt Transformer; Potential transformer
S; E; R Special effect weed; Emerging weed; Ruderal and agrestal
LEGAL STATUS
INVASIVE STATUS
BIOLOGICAL CONTROL
Biological control agents available; control substantial
Biological conrol agents available; control negligible
Biological control agents available; control not determined or under evaluation
Degree of biological control after Klein (2011) and updated 2018 Complete: no other control measures are needed to reduce the weed to acceptable levels, at least in areas where the agents have been established Substantial: other methods are needed to reduce the weed to acceptable levels, but less effort is required (e.g. less frequent herbicide application or less herbicide needed per unit area) Negligible: in spite of damage inflicted by the agents, control of the weed remains entirely reliant on the implementation of the other control measures Not determined: either the release of the agents has been too recent for the meaningful evaluation, or the programme has not been evaluated
PE Prince Edward Isles only
NEMBA category 1a: Requiring immediate compulsory control
NEMBA category1b: throughout South Africa/in part of South Africa Must be controlled or eradicated where possible
NEMBA category 2: throughout South Africa/in part of South Africa Allowed only in specified areas under controlled conditions
NEMBA category 3: throughout South Africa/in part of South Africa Must be controlled within riparian areas; no further cultivation allowed
POTENTIAL THREAT OR IMPACT
by Lesley Henderson
A complete guide to restricted invasive alien plants in South Africa, including another 40 taxa invasive in that region
INVASIVE ALIEN PLANTS IN SOUTH AFRICA
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by Lesley Henderson
Copyright © 2020 Agricultural Research Council. All rights reserved. Permission is granted to Department of Environment, Forestry and Fisheries of South Africa to reproduce this publication or any part thereof for non-profit purposes and with full acknowledgement to the author and publisher.
ISBN: 978-0-620-86146-5
Artists: Major Contributors Marietjie Steyn Wilma Roux Sandie Burrows Gill Condy Rita Weber
Photographers: Major Contributors Lesley Henderson Geoff Nichols
Design and layout: Mac Image
Printing and binding: Novus Print
Sponsor: Department of Environment, Forestry and Fisheries of South Africa: Natural Resources Management Programmes (DEFF: NRMP)
INVASIVE ALIEN PLANTS IN SOUTH AFRICA
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CONTENTS
INVASIVE STATUS .................................................................................................... 14
CONTROL METHODS .............................................................................................. 16
Example page ........................................................................................................... 18
Symbols used ............................................................................................................ 19
Aquatic and Wetland Plants ...................................................................................... 36
Marine Plants ............................................................................................................. 54
NATIONAL LISTS OF INVASIVE PLANT SPECIES ................................................... 310
BIOLOGICAL CONTROL AGENTS ......................................................................... 343
GLOSSARY ............................................................................................................. 358
ABOUT THE AUTHOR ............................................................................................ 382
QUICK GUIDE (INSIDE BACK COVER) ............................................................... 384
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FOREWORD
The impacts of invasive plants cannot be over-emphasised: • They are the single biggest long-term threat to our water security. If our catchments are invaded by pines, wattles, hakea and other thirsty invasives, water security will collapse. • South Africa is the third-most species-rich country in the world. Invasive species are the single biggest threat to our exceptional biological diversity. • They exacerbate wild fires, many invasive species burning at ten-fold the intensity of the species that they displace. • They exacerbate erosion, siltation of rivers and dams, sedimentation and poor water quality, mudslides and flooding.
For these reasons, South Africa has among the world’s most comprehensive programmes to address the problems of invasive species: • It is led by the Working for Water programme (now in its 25th year), through which about 50,000 people are employed to control invasive species. • South Africa is at the forefront of biological control research and application, finding the natural enemies of invasive plants, and ensuring that it is safe to release them in our country. • The Biosecurity Unit is strengthening our capacity to prevent the introduction of potentially invasive species; tackling emerging invasive species (before they become widespread), and enforcing our legislation on alien and invasive species. • The Value-Added Industries programme is utilizing invasive biomass for building materials, furniture and other products, freeing up budget to address priorities such as biological control, clearing of high-altitude areas and early detection of emerging species.
As important as is this work, so much more needs to be done. South Africa will need the active engagement of its citizens, if it is to contain the threat of invasive species. It is each of us who must be aware of the risks of moving species to areas in which they do not occur, and to manage invasive species that are under our control.
With so many invasive plant species already in our country, and a high risk of further invasions (including species that will become invasive as the climate changes), a first step is to be able to identify them. Lesley Henderson’s comprehensive revision of her seminal “Alien Weeds and Invasive Plants”, published in 2001, is greatly welcomed. This beautifully illustrated book, with its apt descriptions, is the product of decades of careful research and field work. It will also be published on-line, in an effort to reach as many key people as possible. It needs to be widely available, for we are all part of the problem – and part of the solution.
May this book inspire more and more South Africans to take the necessary steps to contain invasive plants. We all owe Lesley Henderson a great deal, for her meticulous and dedicated work.
Dr Guy Preston Deputy Director-General Department of Environment, Forestry and Fisheries
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INTRODUCTION
The main objective in producing this book is to enable members of the public and law enforcement officers to identify the restricted invasive alien plant species in South Africa covered by the “NATIONAL ENVIRONMENTAL MANAGEMENT: BIODIVERSITY ACT (NEM:BA) 2004” (Act No. 10 of Republic of South Africa 2004). The book includes a further 40 taxa invasive in this region, some of which have been proposed for listing in the regulations but require further assessment. The book also represents the culmination of the second phase of a mapping project, the Southern African Plant Invaders Atlas (SAPIA), which was started in 2006 and ended in 2016. The plants described in this book are alien or non-native species. All have been introduced into South Africa, either intentionally or unintentionally and with the exception of a few, have either escaped cultivation or become naturalised i.e. are capable of reproducing and spreading without the direct assistance of people. Some species are largely confined to places of severe human disturbance and are classified as ruderal weeds (of waste places) and agrestal weeds (of cultivated lands). By far the majority of species in this book are invaders of natural and semi-natural habitats and they are classified as environmental weeds or invaders. The most serious environmental weeds are transformers which are capable of altering the structure, integrity and functioning of entire ecosystems. Many species described in this book are grown either commercially on a large or small scale, or are cultivated in parks and gardens. Their inclusion in this book does not automatically brand them as undesirable plants which should be eradicated in all situations. On the contrary many are extremely valuable plants under cultivation, such as the eucalypts, pines and wattles. The same plants, however, are considered undesirable when they grow in places where they were not intended, particularly in conservation areas and along water- courses. This book has been built upon a previous publication: ‘Alien weeds and invasive plants’ by L. Henderson (2001). The full reference to this publication and other sources of information are given in the Chapter: OTHER SOURCES OF INFORMATION. The GUIDE TO IDENTIFICATION OF THE SPECIES is sub-divided into six major sections: grasses, reeds and grass-like plants (26 taxa), aquatic and wetland plants (30 taxa), marine plants (3 taxa), herbs (84 taxa), climbers and scramblers (38 taxa) and trees and shrubs (242 taxa). Sub-categories within sections provide further assistance in identification. The species appear in alphabetical order within each sub-category. A QUICK GUIDE to the identification of invaders has been placed inside the back cover for easy reference. This guide will assist the reader in locating a species within the book based on characteristics that are always visible.
Botanical names are mainly according to the Plant List (www.theplantlist.org) and US National Plant Germplasm System: GRIN Taxonomy (https://npgsweb.ars-grin.gov/gringlob- al/taxonomybrowse.aspx).
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The text includes the botanical name (and synonym where applicable), English common name, family, short diagnostic description with important features underlined, cultivated use, habitats invaded and region of origin. Species that are known to be poisonous or irritant are noted. Where two or more species are very similar one species is illustrated and their distinguishing features given in the text. Species distribution maps indicate all known sites where a species has been recorded according to information in the SAPIA database which includes surveys by the author dating back to 1979. Where there were obvious gaps, additional records were obtained from the literature and Botanical Database of Southern Africa (BODATSA) (http://posa.sanbi.org/ sanbi). Some of these records predate 1979. Full details of the localities and dates of recording are available from BODATSA and the SAPIA Database (see OTHER SOURCES OF INFORMATION). Symbols indicate the legal and invasive status, potential impacts or threats, harmful properties and degree of biological control of each species.
Legal status refers to the listing of the species in the regulations under NEM:BA. See RESTRICTED SPECIES AND NEM:BA for the full regulations concerning the control, propagation and trading of these species. Invasive status will enable the reader to differentiate between the species based on different levels of invasiveness. This will also assist managers in deciding on priorities for weed control. See INVASIVE STATUS for a discussion of the terms used. Potential impacts or threats to biodiversity, water resources, fire regimes, agriculture, forestry, tourism and recreation give an indication of some of the negative effects which can result from invasions by the species. See IMPACTS OF INVASIVE SPECIES for more information on this subject. Poisonous, irritant and injurious properties to humans and animals provides further motivation for the control or eradication of invasive plants. The plant parts which are most poisonous or irritant are underlined and the human or animal parts that are affected are given in brackets. Biological control using natural pests and enemies is indicated for those species for which a control programme has been initiated. See BIOLOGICAL CONTROL AGENTS for a table of biological control agents which are established in South Africa and the damage which they inflict on their target host plants. For more information consult the literature and addresses given under OTHER SOURCES OF INFORMATION.
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ACKNOWLEDGEMENTS
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biennis, Parkinsonia aculeata, Parthenium hysterophorus, Pennisetum purpureum, Phytolacca dioica, Pittosporum undulatum, Populus deltoides, P. nigra var italica, Rivina humilis, Rubus cuneifolius, Rubus fruticosus, Schinus molle, Senna bicapsularis, Senna corymbosa, S. didymobotrya, S. hirsuta, S. multiglandulosa, S. occidentalis, S. pendula, S. septemtrionalis, Sorghum halepense, Sphagneticola trilobata, Syzygium cumini, Tipuana tipu, Toxicodendron succedaneum, Trichocereus spachianus, Triplaris americana. Most photos are by Lesley Henderson and the remainder by the SANBI personnel already mentioned and the following people whose names appear next to their photos: Special thanks to Geoff Nichols who contributed photos of 83 species. Rob Anderson, Tom Anderson, Joe Balciunas, Ignacio Barbara, Michail Belov, Richard Boon, Nollie Bosman, Ivan Boyd, Pat Breen, Paul Champion, Carina Cilliers, Krissie Clark, Francois de Wet, Lyn Fish, Sipke Gonggrijp, Niek Gremmen, Adriaan Grobler, John Hoffmann, John Hosking, Fiona Impson, Invasive Species South Africa (ISSA), Trevor James, Jesse Kalwij, Jan-Hendrik Keet, Hildegard Klein, Donovan Kotze, Louise Kritzinger, Volker Kummer, Peter le Roux, Vusi Lubisi, Grant Martin, Peter Meininger, Cliff Moran, Stefan Neser, Tessa Oliver, Lukas Otto, Petr Pyšek, RG & FJ Richardson, Willie Riemsma, Geoff Sainty, Ros Shepherd, Cedric Singo, Louise Stafford, Adrie van Heerden, Kasey Voges, Philip Weyl, Alan Wood, Helmuth Zimmermann. The following photographers made their photos available through Wikimedia Commons: P Clarke, Fibonacci, Christian Fischer, Jerzy Opiola, Pancrat, Sten, Thesurvived99, Samuelistok, Frank Vincentz. Thanks to Petros Ngwenya and Henry Hlela, for providing some isiZulu names, and Kanyisa Jama for providing some isiXhosa names; Graham and David Harding for their contribution towards the chapter on ‘Control’; David Le Maitre for his contribution towards the chapter on ‘Impacts’; Hildegard Klein for information and advice on biological control; Costas Zachariades for providing the 2018 updated catalogue of biological control agents and their host plants, and Philip Ivey for comments on the manuscript. Thanks to the sponsor who made this publication possible: Department of Environment, Forestry and Fisheries of South Africa: Natural Resources Management Programmes (DEFF: NRMP)
Southern African Plant Invaders Atlas (SAPIA) Many thanks to all SAPIA participants and assistants over the past three decades of this mapping project. Special thanks to Pitta Joffe, Hildegard Klein and Lin Besaans for their assistance with roadside surveys across the length and breadth of South Africa which have provided the bulk of the data in the SAPIA database
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IMPACTS OF INVASIVE SPECIES
Alien plants have invaded nearly 80 000 km² of land in South Africa with well-known impacts on hydrology, nutrient cycling and fire regimes. Less well-studied are impacts on biodiversity, the economy and human society. Few studies have been done of the impacts of individual species but these enable us to predict the potential threats or impacts of other species and this has been done in this book.
Biodiversity: • Reduced native species diversity. Invasive alien species threaten the existence of native species through competition and displacement, through hybridization, and by altering water, nutrient and fire regimes. The great majority of the species described in this book are invaders of natural and semi-natural habitats and are a threat to South Africa’s unique, and very special native biodiversity. All the major natural vegetation types or biomes have been invaded by alien species with the most heavily invaded being the Fynbos (roughly coincident with The Cape Floral Kingdom), Savanna and Grassland.
Pompom weed, Campuloclinium macrocephalum,
invading grassland.
Changes in species composition (e.g. Acacia invasion in fynbos) results in the loss of Proteaceae with canopy stored seed in regeneration after clearing; nitrogen enrichment favours alien species. Pine invasions have less severe but similar effects.
Rooikrans, Acacia cyclops, invading coastal fynbos.
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Water resources: • Increased evapotranspiration by floating aquatics.
Water loss through evapotranspiration from a dense cover of water hyacinth,
Eichhornia crassipes, may be three to seven times as much as from
an open water surface.
• Increased evaporation leading to reduced water runoff in catchments and reduced water flow along rivers caused mainly by stands of woody species.
Dense black wattle (Acacia mearnsii) invasion is estimated to result in a 90–100%
reduction in annual river flows. Riparian invasions use water in
rivers and use can exceed the rainfall.
• Altered water quality due to litter and nutrient inputs and changed aquatic communities. • Reduced water storage of wetlands, increased siltation, narrowing of water channels and flooding caused by reeds, willows and poplars. • Disruption of water transport, irrigation and hydroelectricity generation by dense mats of submerged and floating aquatics. • Damage to infrastructure during floods caused by dislodged trees and branches e.g. willows, poplars and acacias.
Giant reed, Arundo donax, narrows water channels.
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Fire: • Increased fire risk due to greater fuel load and flammability of invasive alien species, particularly acacias, pines and eucalypts, but also grasses and reeds. • Increased risk of soil erosion due to water repellency and severe fires leaving only loose mineral soils.
Cluster pine, Pinus pinaster, forms highly flammable
stands in fynbos.
increases the risk of fire in semi-arid karoo.
Soil erosion: • Accelerated river bank erosion caused by stands of shallow-rooted woody species which do not stabilise the banks; dense canopies also shade out stabilising understorey vegetation.
River bank erosion.
• Coastal erosion caused by changes in sand dune dynamics by extensive stands of Acacia cyclops and A. saligna.
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Agriculture: • Reduced agricultural productivity through competition with crops. • Reduced grazing capacity through altered rangeland species composition. • Obstructed access to grazing and water. • Economic losses due to poisoning and injuries to livestock.
Honey mesquite, Prosopis glandulosa var. torreyana,
replacing grazing land in the Northern Cape.
Human and animal health: • Death and injuries caused by plants which are toxic, irritant or spiny.
Famine weed, Parthenium hysterophorus,
reactions in humans and animals.
Toxicity and photosensitization
caused by consumption of lantana, Lantana camara.
• The creation of breeding sites for vectors of human and animal diseases, such as malaria, by mats of invasive aquatics.
Bongani Mashele
Mike Wells
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Forestry: • Reduced growth and productivity due to competition with invasive alien species. • Obstructed access to plantations.
Invasion of pine plantations by bugweed, Solanum mauritianum.
Recreation: • Obstructed access to waterbodies by mats of aquatics, reeds and other dense stands of invaders. • Interference with water sports such as fishing and boating activities.
Invasion of the aquatic plant, water hyacinth, Eichhornia crassipes,
at the Kleinfontein Dam, Benoni in Gauteng Province.
Tourism and aesthetics: • Reduced eco-tourism revenue due to biodiversity loss and high visual impact of invasive alien species in conservation areas and places of scenic beauty.
Firethorn, Pyracantha angustifolia, invading grassland in the Free State.
Lukas Otto
INVASIVE STATUS
Most of the plants in this book invade and persist in natural or semi-natural habitats and are environmental weeds. Some species invade mainly sites of severe human disturbance and are classified as ruderal and agrestal weeds. Invasive status refers to the current status or potential status if this should differ. The categories of environmental weeds are the same as those used in the previous book ‘Alien Weeds and Invasive Plants’ by Henderson (2001), and after J.T. Swarbrick (Plant Protection Quarterly 6(4),1991).
Transformers Plants which can as monospecies dominate or replace any canopy or subcanopy layer of a natural or semi-natural ecosystem, thereby altering its structure, integrity and functioning. Most of these species have been recorded in the SAPIA database as very abundant, forming extensive stands in one or more places. The most serious environmental weeds are in this category, which includes trees, aggressive climbers, thicket-forming shrubs and dense herbs.
Potential transformers Plants that are invading natural or semi-natural habitats, and have the potential to dominate a vegetation layer but not yet having a marked effect. Most of these species are either transformers elsewhere in the world or are showing signs of this ability in South Africa. Most of these species have been recorded in the SAPIA database as abundant in natural or semi-natural habitats.
Special effect weeds Plants which can as monospecies significantly degrade the value or purpose for which a natural or semi-natural ecosystem is valued without necessarily dominating it or greatly altering its vegetational structure or functioning. Examples include weeds which compete with and replace similar native plants, are of high visual impact, poisonous, or chemically irritate users of the area through allergens or stings.
Emerging weeds Plants which are relatively new weeds and have emerged since the late 1990s. Some of these plants have been listed as category 1a under NEM:BA and have been targeted for eradication.
Ruderal and agrestal weeds Mostly annual or biennial plants which are mainly weeds of waste places (ruderals) and cultivated lands (agrestals). They are only able to invade and persist in severely and recently disturbed areas. They scarcely invade or persist in established vegetation. Some species can invade natural or semi-natural habitats along watercourses which are subjected to periodic flooding (a natural disturbance).
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Balloon vine, Cardiospermum grandiflorum: transformer in forest.
Boxing-glove cactus, Cylindropuntia fulgida var. mamillata: transformer in karoo. Photo taken prior to successful
biological control.
CONTROL METHODS
The success of any clearing operation depends on the correct selection of control methods. As there are many types of plants, the chosen method needs to take into account the different growth forms, growth habit and means of reproduction. Other factors to consider include the size of the area to be cleared, the size of the plant and the environment in which it occurs.…